The process of hydroforming metal structural components is well known. See, for example, U.S. Pat. Nos. 5,107,693, 5,233,854, 5,333,775, 4,567,743, 5,070,717, 5,239,852 and 5,339,667, the disclosures of which are hereby incorporated by reference. In a conventional hydroforming process, a tubular metal blank member, typically a piece of sheet metal formed into a generally cylindrical tube, is placed into a die cavity of a hydroforming die. Opposite ends of the tube are sealed, and fluid is injected under pressure internally to the tubular blank so as to expand the blank outwardly into conformance with the interior surfaces defining the die cavity. In more recent improvements to the conventional hydroforming process, opposite ends of the tubular blank are compressed longitudinally toward one another during outward expansion of the tube so as to replenish the wall thickness of the metal as it is expanded outwardly. An exemplary process for replenishing material by longitudinally compressing the blank is disclosed in U.S. Pat. Nos. 5,899,498, 5,855,394, and 5,718,048, and commonly-assigned U.S. patent application Ser. No. 09/061,094 filed Apr. 16, 1998 and Ser. No. 08/915,910, filed Aug. 21, 1997, the disclosures of which are hereby incorporated by reference.
An advantage to hydroforming tubular parts is that parts having varying irregular cross-sectional configurations can be made quite easily, which would be extremely difficult if not impossible to accomplish using roll-forming techniques.
In the conventional hydroforming processes, the final hydroformed component will have a wall thickness that is substantially constant throughout the component or, if it varies at all, such variation cannot be easily controlled, particularly to address situations where significant variations in wall thickness is desired. Subsequent processing of the component or intended applications of the component can create the need for localized increased strength or stiffening. Under conventional hydroforming techniques, a thicker tubular blank can be used to accommodate localized strength requirements, so that the overall thickness of the formed part is determined by the greatest localized strength requirements. Such components are, however, unnecessarily heavy, and material costs for forming such components can become unnecessarily high.
A hydroforming technique for accommodating localized strength requirements is discussed in U.S. Pat. No. 5,333,775, the disclosure of which is hereby incorporated by reference. The ""775 patent discloses a method of manufacturing certain portions of a hydroformed member stronger than others by providing plural tubular blank portions of different wall thicknesses welded end-to-end, so that the completed hydroformed member will have a greater wall thickness at desired locations. The method disclosed in this patent is, however, rather tedious and is thereby process-intensive and expensive.
Other methods have proposed to provide a localized exterior sleeve in surrounding relation to an inner tubular blank. The inner tubular blank is expanded until it engages the interior surface of the exterior sleeve, whereupon further expansion of the inner tubular blank causes concurrent expansion of the exterior sleeve until the exterior sleeve is moved into engagement with the surface defining the hydroforming die cavity. While the exterior surface may provide localized reinforcement, it entirely surrounds the inner tube and thus again provides more metal material than what may be desired. In addition, because the exterior sleeve surrounds the inner tube, it may inhibit desired expansion of the blank, particularly where the hydroformed tube is to be expanded into a corner, and particularly where high gauge metal is desired for the reinforcement.
The foregoing drawbacks of conventional hydroforming processes are overcome in accordance with the concepts of the present invention in which a tubular blank to be hydroformed is locally reinforced in such a manner as to accommodate localized strength or stiffening requirements. In particular, the forgoing drawbacks are overcome by a method of hydroforming a reinforced tube which includes the steps of providing a metal tubular blank having an interior defined by an inner surface and an exterior defined by an outer surface. A metal reinforcing member is provided and inserted into the interior of the tubular blank. The reinforcing member is engaged with the inner surface of the tubular blank and is attached to the inner surface of the tubular blank. The tubular blank and reinforcing member welded thereto are placed into a hydroforming die having die surfaces defining a die cavity, and pressurized fluid is provided within the tubular blank so as to conform the tubular blank with the die surfaces of the die cavity.
The forgoing disadvantages are also overcome in accordance with aspects of the present invention by a method of hydroforming a vehicle frame member. Sheet metal is formed into a generally conical tubular configuration and is seam-welded to form a generally conical tubular blank. The conical tubular blank is placed into a hydroforming die having die surfaces defining a die cavity, and pressurized fluid is provided within the conical tubular blank so as to conform the conical tubular blank into conformity with the die surfaces of the die cavity. A second tubular blank is placed into a second die cavity, and pressurized fluid is provided within the second tubular blank so as to conform the second tubular blank into conformity with surfaces defining the second die cavity. After conforming the conical tubular blank and the second tubular blank, one end of the conformed conical tubular blank is welded to one end of the second tubular blank.
In accordance with another aspect of the present invention, a generally flat reinforcing member is attached to a surface of a generally flat metal sheet to form a composite sheet. The composite sheet is formed into a reinforced tubular blank, and the reinforced tubular blank is placed into a hydroforming die and thereafter conformed to die surfaces of the die.
According to still another aspect of the present invention a hydroformed part including hydroformed tubular member and a metal reinforcing member attached to a surface of the hydroformed member before a hydroforming process. Thus, the reinforcing member is also hydroformed to maintain conforming contact with the hydroformed tubular member.
Other objects, features, and characteristics of the present invention, as well as the methods of operation of the invention and the function and interrelation of the elements of structure, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this disclosure, wherein like reference numerals designate corresponding parts in the various figures.